Field
Certain embodiments generally relate to communication systems, and for example, to device-to-device (D2D) communication integrated into a communications network, such as long-term evolution (LTE) or long-term evolution advanced (LTE-A) cellular network specified by the 3rd Generation Partnership Project (3GPP).
Description of the Related Art
Two types of communication networks include cellular networks and ad hoc networks. A cellular network is a radio network made up of one or more cells, where each cell is served by at least one centralized controller, such as a base station (BS), a Node B, or an evolved Node B (eNB). In a cellular network, a user equipment (UE) communicates with another UE via the centralized controller, where the centralized controller relays messages sent by a first UE to a second UE, and visa-versa. In contrast, in an ad hoc network, a UE directly communicates with another UE, without the need of a centralized controller. Utilizing a cellular network versus an ad hoc network has certain benefits and drawbacks. For example, utilizing a cellular network over an ad hoc network provides the benefit of easy resource control and interference control. However, utilizing a cellular network over an ad hoc network also provides the drawback of inefficient resource utilization. For instance, additional resources may be required in a cellular network when the two UEs are close to each other, as compared to an ad hoc network.
A hybrid network utilizes both a cellular mode and a D2D transmission mode. In a hybrid network, a UE can choose to communicate either via a cellular mode or a D2D transmission mode. As an example, a hybrid network may allow UEs to communicate either via a cellular mode (i.e., via a centralized controller) or via an autonomous D2D transmission mode where the UEs can establish a channel without the need for a centralized controller. The UE can make this selection depending on which mode provides better overall performance. Thus, a hybrid network can improve total system performance over a cellular network or an ad hoc network. However, in order to utilize a hybrid network, issues related to resource sharing and interference situations may need to be addressed.
In addition, there are some situations in which cellular networks may not be available because they are off-line. For example, in a disaster or catastrophic situation, cellular networks may be knocked off-line for various reasons. However, reliable communications networks may be even more necessary in these disaster situations to help alleviate damage and coordinate emergency responses.